Snapshots can be freed through reverse computing in NiLang. Reverse computing has subtle relationship with checkpointing, see author's blog: https://nextjournal.com/giggle/reverse-checkpointing .

I think the core idea is that it actually gives you an inverse function, based on your regular (in the DSL) function definition.

There's as far as I can tell no inherent need to call the regular function first - given any function f, you get a callable inverse function ~f.